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                [Usaco2009 Feb]Revamping Trails 道路升级                </h1>
                <p>时间限制：10s&nbsp;&nbsp;&nbsp;&nbsp;&nbsp;  空间限制：64MB</p>			</div>
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                                <h3>题目描述</h3><p><p><span style="font-size: medium">每天,农夫John需要经过一些道路去检查牛棚N里面的牛. 农场上有M(1&lt;=M&lt;=50,000)条双向泥土道路,编号为1..M. 道路i连接牛棚P1_i和P2_i (1 &lt;= P1_i &lt;= N; 1 &lt;= P2_i&lt;= N). John需要T_i (1 &lt;= T_i &lt;= 1,000,000)时间单位用道路i从P1_i走到P2_i或者从P2_i 走到P１_i 他想更新一些路经来减少每天花在路上的时间.具体地说,他想更新K (1 &lt;= K &lt;= 20)条路经，将它们所须时间减为０．帮助FJ选择哪些路经需要更新使得从１到N的时间尽量少. </span></p></p><hr/><h3>输入格式</h3><p><p><span style="font-size: medium">* 第一行: 三个空格分开的数: N, M, 和 K * 第2..M+1行: 第i+1行有三个空格分开的数：P1_i, P2_i, 和 T_i </span></p></p><hr/><h3>输出格式</h3><p><p><span style="font-size: medium">* 第一行: 更新最多Ｋ条路经后的最短路经长度．</span></p></p><hr/><h3>样例输入</h3><pre>4 4 1
1 2 10
2 4 10
1 3 1
3 4 100
</pre><hr/><h3>样例输出</h3><pre>1

</pre><hr/><h3>提示</h3><p><p><span style="font-size: medium">K是1; 更新道路3-&gt;4使得从３到４的时间由１００减少到０. 最新最短路经是1-&gt;3-&gt;4,总用时为１单位. N&lt;=10000</span></p></p><hr/><h3>题目来源</h3><p>Gold</p>
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